Testing Interfaces

Testing interfaces allows you to troubleshoot problems and to check the quality of links at various layers in the interface stack. The router supports the following test options:

Sending BERT Patterns

The router can send BERT patterns from different layers in the interface stack. For a list of the modules that support bit error rate tests (BERTs), see ERX Module Guide, Appendix A, Module Protocol Support.

To send BERT patterns:

  1. Select a controller.
  2. Configure a specific layer in the interface to generate BERT patterns.

    For information about BERT patterns, see References.

path ds1|e1 bert

path ds3 bert

path ds3 t1 bert

Receiving BERT Patterns

The router can receive BERT patterns from a remote device at the T1/E1 over SONET/SDH VT and T1/E1 over T3 layers. To receive BERT patterns, configure the interface on the router for network payload loopback and the remote interface to use the line clock. Inaccurate results might occur if you use other loopback modes or clock sources.

When the router is synchronized with and receiving BERT patterns from a remote device, the router records the number of bit errors and the number of bits received. To view these statistics, issue the show controllers sonet command.

Enabling Local or Network Loopback

You can enable loopback tests on the router at the following layers in the interface stack:

See Interface Stack for a description of the layers.

To enable local or network loopback:

  1. Select a controller.
  2. Configure local or network loopback at the desired layers in the interface.

loopback

path ds1|e1 loopback

path ds3 loopback

path ds3 t1 loopback

Enabling Remote Loopback Testing

You can configure the router to request that compatible devices connected at the following layers enter into a loopback:

You can also configure the router to start loopback testing when it receives an appropriate signal from a devices connected at any of these layers.

For a list of the modules that support remote loopback, see ERX Module Guide, Appendix A, Module Protocol Support.

Note: There is no protocol that allows remote loopback on E1 links.

To enable remote loopback:

  1. Select a controller.
  2. Configure remote loopback at the desired layers in the interface.

path ds1|e1 loopback remote

path ds1 remote-loopback

path ds3 equipment loopback

path ds3 loopback remote

path ds3 t1 loopback remote

path ds3 t1 remote-loopback

Testing Connectivity

Use the path overhead j1 command to check for connectivity between the router and a SONET/SDH device at the other end of the line. This command defines:

When you define a message that the interface sends, you must monitor receipt of that message at the remote end.

When you define a message that the interface expects to receive, you should configure the remote device to transmit the same message to the interface. You can then use the show controllers sonet command to compare the expected and received messages.

path overhead j1